[2001 ZTS]

Around this time of year the gas stations are changing from a winter blend to a summer one and you mentioned getting gas, your car/ECU may just be getting used to the change maybe? Top up with gas from a different station if possible and maybe a higher grade.

Then there is the old DPFE thing depending on what year your car is.

With temperatures being all over the place this time of year there is consdensation issues within the tank too.

That is all I got I am afraid.